Remote control system



H. o. PETERSON 2,165,502

July 11, 1939.

REMOTE CONTROL SYSTEM Filed June 19, l955 2 Sheets-Sheet 1 (0/1/7301 7 NETWORK INVENTOR H.O. PETERSON ATTORNEY J y 11 1939. H. 0.. PETERSON 2 165 502 REMOTE CONTROL SYSTEI Filed June 19, 1935 2 Sheets-Sheet 2 815M075 Cf/WR/Il 32 OFF/(2 REMOTE CZ'NTRAL OFF/CE INVENTOR H.0. PETERSON ATTORNEY Patented July 11, 1939 UNITED STATES 2,165,502 REMOTE CONTROL SYSTEM Harold 0. Peterson,

River-head, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application June 19,

1 Claim.

The present invention relates to receiving systems, and particularly to such of these as may be controlled from a remote point.

In present commercial radio communications practice, the radio receiver is usually situated at a location particularly free from local disturbances and chosen for its good conditions of reception. For the sake of expediency in the handling of trafiic, the operator is usually situated at a central ofiice located in the city or at a point conveniently accessible to the consumers of the service rendered. "As an example, one of the large communication companies has built a receiving station at Riverhead, New York, where receiving conditions are particularly good; however, the operator who copies the signals is situated in a central office in New York city. The function of the receiving station at Riverhead is merely to select the desired radio signal, amplify it, and convert it to a form of electrical energy suitable for transmission over a connecting link between Riverhead and New York, this connecting link being, in this case, a pair of wires in a telephone cable. At present the receiving apparatus at Riverhead is maintained in proper ad justment by men stationed at Riverhead who receive instructions over an order wire. Due to drifts in transmitter frequency and diurnal variations of signal intensity, it is usually necessary for the receiver attendant at Riverhead to make numerous adjustments of his receiver during the course of a day.

An object of the present invention is to enable the operator at the central oflice to make the most important of the adjustments necessary at the remote receiver, thus relieving the receiver attendant of a considerable portion of his Work.

The two major adjustments required to be made on a receiver after it has been tuned to a given circuit are gain'control and heterodyne frequency control. With the degree of frequency stability-now attained in modern transmitters, it should not be necessary to return the'radio frequency amplifier stages of the receiver during the course of a days running on agiven channel. In the system of the present invention, it is proposed to adjust the receiver gain by means of an automatic volume control arrangement, while the heterodyne frequency control is manipulated through remote control mechanism by the operator at the central ofiice, whereby the adjustment may be maintained at all times at a point which gives best results.

A better understanding of the invention may be had by referring to the following description 1935, Serial No. 27,319 (Cl. 250-20) which is accompanied by drawings, wherein Figs. 1 to 3 illustrate different embodiments of the invention.

Fig. 1 shows a schematic diagram of the complete system. The signal is received on antenna I 5 and amplified by radio frequency amplifier 2. A heterodyne detector unit 4 converts the signal to an audio frequency beat note. The heterodyne oscillator of this unit may be varied over a discrete band of frequencies by means of trimmer l0 condenser 3. The beat note is amplified in amplifier 5 and passed through a low pass filter 6 which has a cut-off frequency approximately the same as that of the tone line l5 over which the signal is transmitted to the central ofilce. In the 15 case of loaded cables, the connecting link may have a cut-off at approximately 2300 cycles. After passing through low pass filter 6, the signal is fed into the connecting link l5 through a level control network 1, from which the signal is sup- 2O plied to a suitable recording device, herein shown by way of example as a headset l4. Signal voltage from the output of low pass filter 6 is also impressed on the grid of rectifier tube 8, which is normally biased to cut-off. The signal applied 25 to detector tube 8 causes it to draw plate current through resistances 9 and I0, thus producing a voltage drop which charges condenser 13 through resistance II and impresses a negative voltage on the control grids of radio amplifier 2, consequent- 3() 1y affording a way of maintaining the output level of the receiver substantially constant irrespective of input signal strength. 7 I In telegraph communications the carrier is absent between characters, and, consequently, if no signal is transmitted between messages, the receiver will be caused to assume a condition of maximum gain by virtue of the automatic volume control arrangement. To enable the receiver to re-adjust itself with maximum speed as soon as transmission is resumed, there is provided an electronic device 12 in parallel with the time constant resistor II. The functioning of this device is adequately described in my'copending application Serial No. 5,734, filed February 9, 1935, Pat- 45 cut No. 2,093,095, dated September 14, 1937, and has been found in practice'to greatly improve the performance of this type of receiver.

The heterodyne frequency control is available at the central ofiice in the form of two push buttons 25 and 26, one ofwhich causes positive current to fiow over the control line I6, and the other of which causes negative current to flow over said line. At the receiving station this current is caused to fiow through the coil of a polar relay I! which is arranged to have its armature stand midway between the two contacts when no current fiows through the coil. If the operator at the central office pushes one of the buttons 25 or 2B, the armature of the polar relay closes a circuit through one of the two electromagnet coils 19 or 20 which causes the rotating shaft from motor l8 to engage with one side of a groove in the wheel 2|, causing that wheel to rotate and drive the frequency controlling condenser 3 through reduction gears 23 and 22. The manner in which the rotating shaft from motor l8 may engage wheel 2| in copending application Serial No. 11,915, filed March 20, 1935. Reversing switch 21 has been provided so that the operator at the central office may control the polarity sent out when a given button is depressed in order thatthe'direction in which the beat note is caused to change may 7 correspond with the markings of the push buttons.

Fig. 2 shows a modification of the remote control device in which control is transmitted through voice frequency carrier channels on the connecting link 29. Since ten or more such voice frequency carrier channels may be simultaneously operated over a single pair of wires, it is apparent that a number of control systems may thus be operated over the same link. When the operator at the central office desires to change the adjustment of the receiver at the receiving station, he may, for instance, depress push button 32 which completes a circuit to energize and close the contacts on relay 33, thus causing tone generator 35 to feed voltage into the line 29 through transmitting filter 31. The frequency of this tone may, for instance, be 255 cycles. At the receiving station the 255 cycle filter 40 selects this voltage, passing it into amplifier rectifier 36 which in turn causes the contacts of relay 38 to close, thus sending battery current through electromagnet 34. Electromagnet 34 operates on the clutch mechanism of the motor driven tuning mechanism and causes an adjustment of the receiver in the desired direction. Control in the other direction is achieved by pushing button 3| which through relay 4| may send out 425 cycle current from tone generator 46 through filter 41 and over the connecting line 29. The 425 cycle energy is selected by filter 42 and amplified at 44, causing the closure of relay 45 and the energization of electromagnet 48.

Fig. 3 illustrates a method whereby one voice frequency carrier channel taining the same effects. In this system the voice frequency carrier channel is periodically interrupted at one of two discrete interrupting frequencies which is selected at the receiving station by a resonant device such as, for instance, a vibrating reed type of relay. By way of illustration we may say the voice frequency carrier channel used is 425 cycles. The interrupting frequencies may be 20 cycles and 30 cycles provided by alternators'or generators and 5!. When the receiving operator'wishes to make an adjustment, he may depress button. 32, which closes interruption frequency generator 50 in series with a battery through the coil of relay 52, causing the contacts of relay 52 to. open and close at the frequency generated by 50. In this way-periodic impulses of 425 cycle voltage from generator 53 are transmitted through transformer "electromagnet 34. is described in greatdetailcan be used for ob- 54 and sending filter 55 into the connecting link 29 to be selected by receiving filter 56 and amplified and rectified by the amplifier rectifier unit 51. Thus, the control energy appears as pulsating direct current through the coil of relay 58. The armature of this relay may be of a vibrating reed construction so proportioned as to resonate at the frequency generated by 50, in which case the armature will vibrate at surficient amplitude to strike the contacts of relay 58 and cause control current to flow through Similarly, if control in the opposite direction is desired, push button 3| would be depressed, sending a different frequency of interruption into relay 59 which interrupts the 425 cycle tone and passes it out over the same circuit to be converted to pulsating direct current at a proper frequency to cause the armature of tuned relay 60 to vibrate and eventually to energize electromagnet 6|. In this circuit it is not necessary to have separate relays 52 and 59, it being possible to connect both generators 50 and 5| to the battery through the coil of one relay.

In the interest of simplicity, the tuning mech anisms of Figs. 2 and 3 have not been shown connected to the receiving circuit elements, although it will be obvious that these mechanisms connect to the same circuit elements shown in Fig. 1. Also, there are provided headphones, not shown, for the circuits of Figs. 2 and 3 which are connected through a line extending from the receiver proper to the remote central office in a manner similar to that shown in Fig. 1.

It is to be understood, of course, that the invention is not limited to the precise details shown and described since various other types of mechanism may be used without departing from the spirit and scope thereof; for example, this type of control mechanism can also be applied to the adjustment of other parts of the receiver or to the adjustment of other apparatus such as transmitters.

What is claimed'is:

In a commercial radio telegraph communication system, a heterodyne receiver for receiving signal waves, a remote control station, utilization apparatus at said remote control station, a wire line extending between said utilization apparatus and said receiver, said line being coupled to the output of 'said receiver, and means for controlling the heterodyne frequency at said receiver, said means including tuning mechanism at said receiver, two generators of oscillations of different audible frequencies at said control station, said tuning mechanism being responsive to said oscillations, a wire circuit extending from said control station to said tuning mechanism, individual normally unenergized relays at said control station for separately effecting the transmission of oscillations from said two generators over said circuit, and separate filters at said control station .and at said receiver for selectively passing the oscillations generated by said audio generators, individual relays at said receiver each operable inresponse to only one of the frequencies passed by said filters for affecting said tuning mechanism, and keying mechanism for selectively operating said relays at the control station, whereby said tuning mechanism at said receiver may be controlled in either of, two senses.

. HAROLD O. PETERSON. 

